The present invention relates to an emission control system for internal-combustion engines in which a purifying insert, e.g. a monolith, is arranged in a housing with an intermediate layer.
In a known emission control system, the catalyst support body used as the purifying insert receives a diagonal flow against a front side, so that, for an optimal flow against the front side, the entire front side is situated in the connection cross-section of the diagonally directed inflow pipe. For arranging the diagonal inflow pipe on a front side of the housing, the inflow pipe has, at least in areas, edge areas of the connection cross-section which are directed transversely with respect to the housing shell. A permanent connection of these edge areas, which partially cross the shell front sides, with the shell of the housing requires high expenditures of effort and cost.
It is an object of the invention to configure the connection of an exhaust gas inflow pipe with the housing accommodating a purifying insert in a simpler manner while a large-surface diagonal flow against the front side of the support body is taken into account.
This object is achieved in accordance with the present invention by providing that the inflow pipe has a section which represents a boundary around the insert downstream of its front side and is used for a connection with the housing.
The arrangement of a housing section on the exhaust gas inflow pipe according to the invention provides a simplified connection of the two components in an advantageous manner while the diagonal flow against the purifying insert is optimal.
With respect to manufacture of the system, the connection is simplified by configuring the connecting section of the inflow pipe as a boundary around the insert with play while, in sections, a flexible intermediate layer is omitted. This free outer circumference section of the insert may have the result that a plastic ring, which during the operation of the internal-combustion engine burns up without any residue, supports in an advantageous manner the center of the connecting section during assembly of the system and in the supporting process may also protect the front edge of the insert.
With a view to an advantageous embodiment which is appropriate for automatic devices, the connecting section of the inflow pipe can have a connecting flange extending transversely to the connection-side front side of the housing. As a result, tight fillet joints for a close material connection can be used which are obtained with low expenditures of material. A correspondingly selected radius between the connecting section and the connecting flange can advantageously facilitate the above-mentioned centering.
The additional suggestion according to the invention of configuring the connection part of the inflow pipe which has the connecting section as a separate funnel results in the advantage that the connecting section can be formed out as a true-to-size housing section.
In another embodiment of the connection, the connecting section of the inflow pipe or of the funnel in the house-side end section has a flange which can be centered on the outer contour of the housing.
For achieving a large-surface diagonal flow against the insert, a pipe, end section of the inflow pipe can be arranged in an opening of the funnel in that it is inserted in such a manner that, by way of the pipe end section which is adjacent closest to the front side of the insert, acting upon the extreme edge area of the front side of the insert is ensured.